diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index acd2d7be844e..4b9fc52b6e31 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-05-16  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/57943
+	* semantics.c (finish_decltype_type): Call
+	instantiate_non_dependent_expr_sfinae on the expression.
+
 2020-05-15  Patrick Palka  <ppalka@redhat.com>
 
 	Revert:
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index d90816eabc94..64587c791c67 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -9746,6 +9746,14 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
 
       return type;
     }
+  else if (processing_template_decl)
+    {
+      ++cp_unevaluated_operand;
+      expr = instantiate_non_dependent_expr_sfinae (expr, complain);
+      --cp_unevaluated_operand;
+      if (expr == error_mark_node)
+	return error_mark_node;
+    }
 
   /* The type denoted by decltype(e) is defined as follows:  */
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 875ac82fb340..a7f777118f26 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-16  Patrick Palka  <ppalka@redhat.com>
+
+	PR c++/57943
+	* g++.dg/cpp0x/decltype76.C: New test.
+
 2020-05-15  Jason Merrill  <jason@redhat.com>
 
 	* g++.dg/coroutines/coro.h: Always #include <utility>.
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype76.C b/gcc/testsuite/g++.dg/cpp0x/decltype76.C
new file mode 100644
index 000000000000..239fe6d2a8f2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype76.C
@@ -0,0 +1,7 @@
+// PR c+/57943
+// { dg-do compile { target c++11 } }
+
+struct a { };
+
+template <typename T = decltype (a(0))> // { dg-error "" }
+void f() { }